1. Field of the Invention
The present invention relates to a packet transfer device, a packet transfer method, a packet transfer program and a communication device.
2. Description of the Related Art
Internet service provider (ISP) provides an environment for connecting an IP network using a network address conversion function disclosed in Non-Patent Document 1, for example.
The method for connecting a network in related art will be described with reference to FIG. 2. In FIG. 2, a user A, a user B and a user C respectively have a contract for a connection with an ISP 114, CPEs (customer premises equipments) 108 to 110 such as a modem for connecting to a router 115 of the ISP 114 are installed in home networks (HNW) 111 to 113 of the respective users A to C.
The CPEs 108 to 110 have a network address conversion function. The network address conversion function is for allocating a single global IP address to a private IP address of user's terminal and managing the relationship between the private IP address and the global IP address so that the terminal can connect to the Internet.    [Non-Patent Document 1] RFC2663